Upgrading ZFS File Systems (zfs upgrade)

Solaris 10 10/08 Release: The zfs upgrade command
is included in this release to provide future ZFS file system enhancements
to existing file systems. ZFS storage pools have a similar upgrade feature
to provide pool enhancements to existing storage pools.

For example:

# zfs upgrade
This system is currently running ZFS filesystem version 3.
All filesystems are formatted with the current version.

Note –

File systems that are upgraded and any streams created from those
upgraded file systems by the zfs send command are not accessible
on systems that are running older software releases.